1. Field of the Invention
This invention relates to valves for internal combustion engines together with means for effecting rotation of such valves to improve the operating life of both the valve and of the valve seat, and to prevent or minimize thermal distortion of the valve in the case of an exhaust valve.
2. Description of the Prior Art
It has been known in the prior art that it is desirable to provide means for rotating the poppet valve of an internal combustion engine about the longitudinal axis of the valve stem in addition to imparting the normal reciprocatory movement to the valve by means of the operating cam, since such rotation of the valve provides for more uniformly distributed wear of the valve head portion and also of the valve seat with which the head portion of the valve cooperates. In the case of an exhaust valve, rotation of the valve effects more uniform heat distribution throughout the valve head and valve stem and thus avoids or minimizes thermal distortion of the valve. Rotation of a poppet valve of an internal combustion engine or the like may be accomplished by providing a construction in which the valve lifter which is engaged by the rotating cam member has its central longitudinal axis offset from the central plane (with respect to the lengthwise dimension of the cam shaft) of the cam which engages the valve lifter. This offset relation of the longitudinal axis of the valve lifter relative to the cam which engages the valve lifter causes the rotating cam to effect a rotation of the valve lifter about its longitudinal axis and thus to effect a rotation of the valve engaged by the valve lifter during the period of cam rotation when the valve is lifted off the valve seat. The cooperation between the cam and the valve lifter of course additionally imparts a reciprocatory movement to the valve lifter and to the valve engaged by the valve lifter. Constructions of the general type just described are shown, for example, by U.S. Pat. Nos. 1,129,555 issued to Stanley Curran on Feb. 23, 1915; 1,470,102 issued to Fred Rahm on Oct. 9, 1923; 1,983,744 issued to Herman Dock on Dec. 11, 1934; and 2,925,808 issued to Karl Bauman on Feb. 23, 1960. Other United States patents related to the problem of providing valve rotation for internal combustion engines include the following: 3,056,394 issued to Ib H. Svendsen on Oct. 2, 1962; and 3,574,304 issued to John D. Santi on Apr. 13, 1971.